Missouri S&T Solar Village Microgrid

The Missouri S&T Solar Village Microgrid Project is a small scale microgrid project, employing alternative and renewable generation, advanced energy storage, and intelligent switching capabilities into a residential facility complex. Located on the Missouri University of Science and Technology campus, the project implemented these technologies in order to more accurately understand the effect and capabilities, microgrid power systems have on small community and residential areas. The advisory board behind the project included interested parties from local utilities, military interests, corporate and federal agencies. This board helped shape the direction of the microgrid project, as well as the technologies adopted and research outcomes expected from the project. The technical design and installation of the microgrid was the largest component of the project, but the social and legal implications of this project were also examined. The Microgrid at Missouri S&T offered a view into the next generation technologies within microgrid power systems, a state of the art testbed for researchers to utilize, and an opportunity to breach some of the legal and societal barriers to advanced power systems within the region.

The Solar Village at Missouri S&T is a series of four U.S. Department of Energy Solar Decathlon homes that the university has built throughout the years of the competition. These four homes reside within a city block within Rolla, and are all grid connected. The motivation to create a microgrid between these homes was to be able to better utilize the solar energy generated on site, to be used locally, rather than exported to the municipal grid. These homes, each with a tenant from the campus community as a student, faculty, or staff member, each have a unique load profile and a discrete power load. These real world loads, in addition to the inherent generation of the solar homes, provide a unique electricity curve for each house and for the village as a whole. An additional load to the microgrid and the village is the installation of an electric vehicle charging station. This will add another real world load to the village’s profile and the effect on the integrated system.

The technologies implemented within the microgrid include solar generation, a natural gas fuel cell, lithium ion battery storage, and automated intelligent switch gear. The update to the village, and the integration of these advance power systems made this microgrid project unique within the residential sector. The solar generation on each house comprised a type of silicon panel either monocrystalline or multicystalline, with a total power generation capable of 21 kW. Each of these 4 arrays used a Fronius grid- connected inverter sized for each array before connecting to the rest of the microgrid. A 5 kW natural gas fuel cell was installed to apply aspects of combined heat and power to the microgrid. The fuel cell, with an integrated hydrogen reformer, used natural gas as its fuel source to generate electricity and had a waste output of low quality heat. The electricity was directed to the microgrid power system, the heat output was directed to the hydronic systems within two of the homes. The heat is used primarily as a supplement to potable water and space heating load. The energy storage system within this project was a total 60 kWh Lithium ion battery. These two 960 Vdc nominal battery racks each had roughly 30 kWh of storage capability. The bidirectional inverter used to charge and discharge the battery racks is also a sizable component to the system. It transformed the 960 Vdc battery voltage to a 120/240 Vac, split phase, to be used within the village and the rest of the microgrid system. The switchgear used within the project is two sets of six automated switches with background programmable scenarios and early adaptable schema. In the first generation, this hardware primarily allowed the microgrid to direct energy to the necessary loads and direct excess energy to the storage, or to the municipal grid. In the next iteration of the software, the time of use, demand response, load shifting, and other scenarios will be integrated to affect microgrid power operations. The technology within this project and the integration of the systems involved have made this a state of the art facility on the Missouri S&T campus.

The legal and social implications of this microgrid were also a challenge to overcome. Rolla, Missouri and its municipal power provider, Rolla Municipal Utilities (RMU), are a partner within a larger power pool. What makes this significant is that the agreements between Missouri S&T and RMU, were only a portion of the negotiations necessary to be able to commission a project like the microgrid. Although both groups were supportive of the project, their need to ensure the microgrid would not endanger their workers, community, or investment was a priority. In particular, the solar generation in Missouri was covered under a renewable energy standard, and was allowed with minimal paperwork and issue, however the natural gas fuel cell because it was a fossil fuel could not be considered as a renewable source, and was not covered under their common practices. This specific issue was eventually resolved through the use of advanced metering, but the negotiations to that point were something that had not been done before at this small of scale. The social effect of this project also come through education and awareness. The village has always hosted many tours to learn about energy and solar homes, but now the microgrid has given the opportunity to teach the community about advanced power systems and the effect one community can have on the much larger grid. From tours to university research, the microgrid at Missouri S&T has the opportunity to educate about the next generation of advanced power systems.